1. Field of the Invention
The present invention relates to a hydrodynamic bearing device. This hydrodynamic bearing device is ideal for use in motors for information technology equipment, including a spindle motor used in a magnetic disk apparatus such as HDD and FDD, an optical disk apparatus such as CD-ROM and DVD-ROM, and a magnetic optical disk apparatus such as MD and MO, and a polygon scanner motor used in a laser printer (LBP), and is also ideal for use in small motors for electrical equipment such as an axial fan.
2. Description of the Related Art
In each of the different types of motor described above, in addition to high rotational accuracy, increased speed, reduced costs, and reduced noise are all keenly sought after performance factors. One of the structural elements which determines these factors is the bearing which supports the motor spindle, and in recent years, the use of hydrodynamic bearing devices which display superior characteristics for the performance factors described above has been the subject of much investigation, and in some cases, these bearings have been used in practical applications.
For example, a construction has been disclosed for a hydrodynamic bearing device for integration within a spindle motor for a disk apparatus (refer to Japanese Patent Laid-Open Publication No. 2002-061636), in which, as shown in FIG. 11, a bearing sleeve 40 is secured to the inner periphery of a housing 30, and an axial member 20 is positioned inside the bearing sleeve 40. In this hydrodynamic bearing device, rotation of the axial member 20 causes pressure to be generated by a fluid dynamic pressure effect in a radial bearing gap between the inner periphery of the bearing sleeve 40 and the outer periphery of the axial member 20, and the axial member 20 is supported in a non-contact state.
In this hydrodynamic bearing device, the housing 30 is formed by sealing the bottom opening of a cylindrical peripheral part 31 with a thrust bush 32. The thrust bush 32 is secured to the bottom opening of the peripheral part 31 using an adhesive, although other methods such as caulking, or a combination of caulking and adhesive can also be used.
In conventional devices, because the housing is formed from a turned metal such as copper, the productions costs for the housing continue to rise considerably. Furthermore, because the bearing sleeve is secured to the inner periphery of the housing using an adhesive, steps are required for applying and then drying the adhesive, making the assembly process more complex, and further increasing the production costs. In addition, because the thrust bush 32 is secured to the peripheral part 31 using an adhesive and/or caulking, as described above, this process also invites further increases in cost.